The degeneration of the intervertebral disk, in particular of the nucleus pulposus, results in a loss of height in the affected disk space which is associated with a weakening of the annulus fibrosus and of the ligaments. The spinal column hereby becomes instable at this position. The consequence is a horizontal displaceability of the vertebral bodies with respect to one another which results in impairments of the nerve roots in this region and/or of the spinal marrow with pain resulting therefrom.
The principle for the treatment of these symptoms consists of the surgical removal of the nucleus pulposus and the insertion of support bodies in order to restore the normal height of the disk space.
There is a variety of demands on spinal implants, and in particular on implants for interbody fusion of the lumbar vertebral column. For instance, on the one hand, a contact surface with the vertebral bodies to be fused should be provided which is as large as possible. This means that, if conventional implants are used, a plurality of implants have to be kept in stock since the required dimensions cannot be determined precisely pre-operatively and since the length and the height of the vertebral bodies varies. Studies have namely shown that the length of the vertebral bodies can fluctuate between 22 and 34 mm and their width can fluctuate between 31 and 49 mm (cf. Ebraheim et al, Anatomic Considerations for Anterior Instrumentation of the Lumbar Spine, ORTHOPEDICS, October 1999, Volume 22 No. 10).
A further demand on spinal implants, and in particular on implants for the lumbar vertebral column, is sufficient and sufficiently predictable compression strength. Furthermore, the spinal implant should, where possible, have the same resilience as the bone, which is not the case with conventional metal implants.
A spinal implant for interbody fusion to the spinal column is known from DE 199 52 939 A1 which consists of a body made from bone material which is curved in the direction of its longitudinal extent.